Various types of machines are known for popping corn and producing expanded foods such as puffed snacks. Some popcorn poppers include a heated surface (e.g., a popping kettle) that heats the corn and causes it to pop. Other popcorn poppers use hot air to pop corn.
A typical flow-through popcorn popper or snack puffer includes a rotating “puffing drum” that consists of a steel auger wrapped in a perforated metal skin. The puffing drum is positioned in a heated cabinet and rotated at a constant speed. Material (e.g., an extruded starch or other snack material) is introduced in one end of the drum, and the auger moves the material through the drum and out the far end. Depending on the type of material, the material can reside in the drum anywhere from about 30 seconds to about 300 seconds. As the material moves through the drum, a high pressure fan blows hot air from an electric heating element or gas burner upwardly through the perforated drum with enough heat and pressure to suspend and fluidize the material. For example, typical air temperatures for popping corn or puffing starch-based snacks within the drum can range from about 400° F. to about 450° F. Approximately 90 percent of the air that is driven upwardly through the drum can be reheated and re-circulated through the drum.
Because of the relatively high number of moving parts, conventional flow-through poppers and flow-through puffers can be expensive to manufacture.